This invention relates generally to a seal assembly and, more particularly, to a check valve seal assembly for a pump.
Piston pumps are known to be used in hydraulically-actuated fuel injection systems. The reliable operation of such pumps and their components is significant to the overall operation of the engine. Moreover, the ability of such pumps and their components to operate free of maintenance is important to reduce downtime of the system. While reliable operation is an important design criteria, issues such as cost and ease of assembly influence the overall design of such pumps and their components.
In some systems, a piston pump pressurizes hydraulic fluid and supplies the pressurized fluid to a common rail, which in turn supplies hydraulic fluid to a plurality of hydraulically-actuated fuel injectors mounted in a diesel engine. The pump displaces high pressure fluid to the common rail via a check valve. The check valve attempts to prevent leakage of displaced high pressure fluid back into the pump during a suction stroke and to prevent leakage of high pressure fluid from an interior of the pump to an exterior of the pump. In order to prevent such leakages, the check valve requires two sealing points: one that prevents the leakage of fluid back into the pump and another that prevents leakage of pressurized fluid to an exterior of the pump.
While the pump may perform well in operation, the force of pressurized fluid created during a piston""s discharge stroke and the vacuum force created during a piston""s suction stroke require that a check valve assembly be manufactured with a tight tolerance and assembled with relatively high precision. Therefore, production of such pumps may be costly and complex.
The present invention provides a seal assembly that avoids some or all of the aforesaid shortcomings in the prior art.
In accordance with one aspect of the invention, a check valve assembly includes a plug having a first end and a second end spaced along a longitudinal axis of the check valve assembly. The check valve assembly also includes a first valve seat, wherein the first end of the plug sealingly contacts the first valve seat. A second valve seat is spaced from the first valve seat in a direction of the longitudinal axis. The check valve assembly further includes a resilient member between the plug and the second valve seat and a spring member urging the resilient member into sealing contact with the second valve seat and the plug.
In accordance with another aspect of the invention, a pump for supplying high-pressure fluid to a hydraulically-actuated fuel injection system for an engine includes a drive shaft configured to receive drive torque from the engine, a drive plate coupled to the drive shaft, and at least one sleeve coupled to the drive plate and having an internal bore. The at least one sleeve is reciprocatingly driven by the drive plate to pressurize fluid. The pump also includes an outlet passage in fluid communication with the internal bore and a check valve assembly configured to allow pressurized fluid above a predetermined pressure to pass through the outlet passage to a collection outlet. The check valve assembly includes two sealed contact regions spaced along an axis of the check valve assembly that prevent leakage through the check valve assembly and that prevent leakage from an interior of the pump to an exterior of the pump.
In accordance with yet another aspect of the invention, a method of assembling a check valve assembly includes coupling a plug with a bore in an outlet passage of a pump housing and sealingly contacting a first end of the plug with a first valve seat defined by the bore. The method further includes urging a resilient member into sealing contact with a second valve seat defined by the bore. The second valve seat is spaced from the first valve seat in a direction of a longitudinal axis of the check valve assembly.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention.